White PapersThe placement of nGenius Probes on the network – where and what type – determines to a large degree what data is collected and sent to nGenius Performance Manager. Probe placement for VoIP focuses on three core areas of the network. The first is the link between the core switch fabric and the Avaya Media server cluster. Placing a probe on the Fast Ethernet link between an IP PBX and a switch collects signaling traffic destined for the campus environment.
The second area for probe placement is on the
Gigabit uplinks between the core switch fabric and work group switches. In a typical campus environment, Gigabit uplinks provide high-speed transmission of voice traffic from edge switches to the core switch fabric, an important aggregation point for voice traffic. The final area of probe placement is the IP WAN.
The IP WAN segments in particular are crucial to monitor since they represent generally the costliest links in the overall network, the most vulnerable to congestion, and the least flexible for the IT department to manage around or affect rapid bandwidth changes. The ability of the nGenius Solution to monitor not only a multitude of WAN technologies, but to see within those segment to the underlying DLCIs and PVCs, give it flexibility in reporting VoIP traffic flows throughout the network.
Optimizing Voice and Data Performancefor Avaya IP TelephonyExecutive SummaryThe nGenius Performance Management solution from NetScout Systems, Inc. is avital tool in helping enterprises manage and optimize their Avaya IP telephony solu-tions. While not replacing the important device and system management tools bun-dled with Avaya"Communication Manager, the nGenius Solution provides a deep-er look into the network, enabling IT managers to compare - in real time- VoIP traf-fic flows with those of other applications to manage bandwidth, set proper QoSpolicies for voice and data applications, capacity plan for future growth, and moreeffectively troubleshoot issues as they arise. This paper demonstrates how the nGenius Solution has the flexibility to identifyand monitor virtually all data applications, converged VoIP applications and set-upprotocols, as well as applications specific to Avaya Communication Manager 2.0.Untitled DocumentA Complementary Approach the nGenius Solutionwith Avaya IP TelephonyThe nGenius Solution, a network and application performance manage-ment system, monitors the enterprise and provides real-time and historicviews on network-based applications. It consists of two components: " nGenius Performance Manager software which is loaded on a server,collects, analyzes and stores statistics from nGenius Probes, flowbased data sources, and standard SNMP MIBs from comparablerouters and switches. Where it is accessible from a web browser, ITprofessionals can use the tool from any location for troubleshooting,application profiling, capacity planning, and response time analysis." nGenius Probes deployed strategically throughout the enterprise LAN,WAN and SAN, collect and send data flow statistics to nGeniusPerformance Manager. With application level visibility, the nGeniusProbes identify and track top talkers and conversations for virtually anyapplication well known, complex, custom, and web-based - as wellas network and link layer details.As it relates to a typical multi-site Avaya Media Server and MediaGateway implementation, the full implementation of the nGenius Solutionwith Avaya Communication Manager might look like the following:Figure 1: An Avaya Communication Manager system with nGeniusPerformance Manager. At the site on the top, the host Avaya MediaServer (or cluster of servers) is equipped with the Media Processor(MedPro). nGenius Probes installed on LAN and WAN segments monitorflow-based data, including call setup protocols and voice media streamtraffic, which is summarized and viewed in nGenius PerformanceManager.Probe Placement to Monitor Voice FlowsThe placement of nGenius Probes on the network where and what type determines to a large degree what data is collected and sent to nGeniusPerformance Manager. Probe placement for VoIP focuses on three coreareas of the network. The first is the link between the core switch fabricand the Avaya Media server cluster. Placing a probe on the Fast Ethernetlink between an IP PBX and a switch collects signaling traffic destined forthe campus environment. The second area for probe placement is on theGigabit uplinks between the core switch fabric and work group switches.In a typical campus environment, Gigabit uplinks provide high-speedtransmission of voice traffic from edge switches to the core switch fabric,an important aggregation point for voice traffic. The final area of probeplacement is the IP WAN. The IP WAN segments in particular are crucialto monitor since they represent generally the costliest links in the overallnetwork, the most vulnerable to congestion, and the least flexible for theIT department to manage around or affect rapid bandwidth changes. Theability of the nGenius Solution to monitor not only a multitude of WAN tech-nologies, but to see within those segment to the underlying DLCIs and PVCs,give it flexibility in reporting VoIP traffic flows throughout the network.nGenius Probes, available in a variety of configurations, can monitor virtu-ally all LAN and WAN topologies in the network, by using the patent pend-ing CDM"Architecture, that enables them to collect and map flow-baseddata to nGenius Performance Manager. LAN-based probes can connect tothe spanning port on an Ethernet switch or passively tap a critical interswitchlink, while WAN probes tap the link on the WAN side of the edge router.In general, probe placement to track VoIP flows does not vary greatly fromthe way the nGenius Solution would normally be deployed to monitorinformation on networked data applications such as ERP, Web, e-mail,Siebel, and Citrix. Shuffling and Hairpinning, two customer selectablefeatures on the Avaya Communication Manager platform, can challengethe collection of voice-related information in a standard nGenius Solutiondeployment. They are discussed in the next section. Management Challenges from Shufflingand HairpinningAvaya Media Server, with its embedded Media Processor card, is theworkhorse of the voice system. In a typical scenario, the Media Serverand MedPro card act in concert to control all aspects of the voice manage-ment, from call setup and teardown, to the voice compression codecs, tothe routing of the call. But as voice RTP packets stream across the net-work over campus hops or the IP WAN - additional latency is addedwhich can noticeably affect end-user voice quality.To work around this, Avaya employs two methods that limit or take themedia processor completely out of the voice communications path.Known as shuffling and hairpinning, these techniques reduce some ofthe delays, jitter and sequencing errors that can occur due to round tripnetwork latency.In call shuffling once a call is established between two IP endpoints on anetwork, the Media Processor, which typically would stay engaged in thecall path, essentially drops out and the RTP packets stream directlybetween the two IP end-points. Only a small signaling channel is keptopen back to the Media Processor in the event a voice feature such asconferencing is invoked by one of the parties. 2IPI PIP P h o n eH E A D Q U A R T E R SR E M O T E O F F I C En G e n i u s P e r f o r m a n c eM a n a g e rn G e n i u s P r o b e sI P W A NP S T NM e d i aS e r v e rM e d i aG a t e w a yI P P h o n eP C R u n n i n g n G e n i u sC o n s o l eM e d i aG a t e w a yUntitled DocumentFigure 2: Call Shuffling works by taking the Avaya Media Processor(embedded in the Avaya Media Server) out of the direct voice path of thecall. By doing so, RTP packets stream directly between two IP endpointson a network segment, bypassing the IP WAN, which introduces addition-al latency and therefore potential voice quality issues. nGeniusProbes onthe proper network segments ensure voice flow data is collected andlogged in nGeniusPerformance Manager.Hairpinning works much the same way as shuffling, except that hairpin-ning involves routing through a gateway between two types of networks,such as IP and analog. Re-routing the voice path so it does not travelacross the TDM bus of the Avaya Media Gateway reduces latency andpotential voice quality issues arising from the movement of voicebetween PSTN and IP mediums. CDM Technology as the Foundation for MonitoringAvaya Voice ProtocolsLike many IP PBX manufacturers, Avaya utilizes a combination of stan-dards-based and proprietary implementations of well-known call setupprotocols in its servers, gateways and IP endpoints. Using the nGeniusSolution to monitor call set up protocols, such as H.323, SIP, and MGCPprovides real-time and historical analysis, side by side with other dataapplications traversing the same links. Avaya takes this further by utilizing a version of H.323 v2 with proprietaryfeature extensions. The difficulty from a management perspective lies intracking the H.323 voice setup apart from other multimedia applicationsthat also use H.323, such as video conferencing. NetScout has workedclosely with Avaya to certify its version of the protocol stack and hasdubbed it Enhanced H.323 or (eH.323). This protocol is included withnGeniusPerformance Manager as a standard protocol.Visibility Into Voice ConversationsThe nGeniusSolution helps IT staff troubleshoot and manage capacityissues in their converged network by monitoring the voice and call set upprotocols as well as tracking voice conversation information. The mediatraffic setup protocol RTCP - communicates call details such as IPaddresses of sender and receiver, call length, call setup time, call quality,latency, packet loss, codecs, and QoS. Strategically deployed nGeniusProbes deployed near the Avaya Media Server, Gateway or close to work-groups of users sees this exchange of call record details throughout thecall and/or at the end of a call and collects these details in an innovativeVoIP Management Information Base (MIB).The VoIP MIB is a multimedia data collection system designed byNetScout for nGeniusProbes. By enabling the VoIP MIB, call conversationstatistics are collected and sent to the nGeniusPerformance Managerwhere they can be viewed in real time, providing an added level of detailfor troubleshooting and configuration of voice users. 3Optimizing Voice and Data Performance for Avaya IP TelephonyIPIP Phonea ll Shuffling: Beforeall Shuffling: AfterM edia Server withM edia Processor (M edPro)T he voice pathtaverses the W ANto get back to theM edia ProcessorIPIP PhoneIP PhoneM edia Server withM edia Processor (M edPro)H .323/SIP callsetup/signaling= Voice PathH.323/SIP callsetup/signalingH.323/SIP callsetup/signalingBy Keeping the RTP voice between twoIP endpoints on the LAN, latency is reducednGenius Probes placed strategically on the network capturevital voice and flows, call set-u and sinalin rotocolsIP PhoneIPIPIP W ANIP W ANShuffling. The process of rerouting the voice channel connect-ing two IP endpoints so the voice completely streams across anIP network without using intermediate CommunicationManager media processor resources.Hairpinning. Rerouting of a voice channel connecting two IPendpoints so that the voice travels through the media processorcircuit pack in IP format, without having to go through thegateway s Time Division Multiplexing (TDM) bus. Only the IPand RTP packet headers are changed as the packet goesthrough the media processor. This requires that both endpointsuse the same codec.Avaya Communication Manager 2.0 and aboveutilizes the following voice-related protocols:" H.323 v2 stack, including- H.225- Q.931- H.245- H.248 (can be used as gateway control)- Proprietary extensions"Real-Time Transfer Protocol (RTP) for audio stream"Real-Time Transfer Control Protocol (RTCP) for signaling"SIP for 3rd party phonesUntitled Document4NetScout Systems, Inc.Corporate Headquarters310 Littleton RoadWestford, MA 01886 USATelephone (978) 614-4000Fax (978) 614-4004Web: www.netscout.comEuropeRegus House268 Bath RoadSlough, Berkshire, SL1 4DX UKPhone: +44 1753 725561Fax: +44 1753 725562Asia/PacificRoom 105, 17F/B, No. 167Tun Hua N. RoadTaipei, TaiwanTelephone +886 2 2717 1999Fax +886 2 2547 7010The nGenius Solution is comprisedof nGenius Performance Manager,nGenius Probes and for specializedsituations, additional appliancesincluding nGenius Flow Collectorand nGenius Flow Recorder. nGenius Performance Manager is a software application that analyzesthe information collected by nGeniusProbes as well as other network devices,and delivers the features and functionsof multiple performance managementdisciplines in a single product.nGenius Probes are hardware monitoringdevices that are the industry s mostadvanced sources for identifying, collecting and analyzing application-level traffic data across the enterprise.nGenius Flow Collectors are dedicatedhardware devices optimized for collectingapplication conversation data viaNetFlow records produced by leadingnetwork infrastructure devices. nGenius Flow Recorder is an appliancethat couples storage for large packettrace captures and graphics-based datamining software. It continuously recordsall traffic and produces a network audittrail for post-event forensics requiringfull packet payload details. 2005 NetScout Systems, Inc. All rights reserved.NetScout and the NetScout logo, nGenius and Quantivaare registered trademarks of NetScout Systems, Inc.The CDM logo, MasterCare and the MasterCare logo aretrademarks of NetScout Systems, Inc. Other brands,product names and trademarks are property of theirrespective owners. NetScout reserves the right, at itssole discretion, to make changes at any time in its tech-nical information and specifications, and service andsupport programs.CC-0193-05 Rev AFigure 3: nGenius PerformanceManager display voice conversationviews that show individual end-userstatistics, including active call, phoneextension, user, host and destination IPaddress, call time, duration and more.Figure 4: Call performance statisticslike jitter, packet loss and differentiatedservices code point (DSCP) are viewedin real time under the Quality tab.The voice conversation statistics areused to identify mis-configured DSCPassignments that impact the quality ofthe call. These statistics can also beused to identify a mistake in the codecin use, abnormally high packet loss, or an increase in calls affected by jitter. While this information is impor-tant in context, it does not replace the management tools bundled with Avaya Communication Manager,rather, the call conversation statistics give enhanced views into troubleshooting operations: who are thebiggest users, conversation time, jitter, packet loss. When used by a cross-functional team of IT and telecomstaff, this information can create actionable intelligence to return a user to service more quickly or even finda problem before it becomes noticeable to the end-user community.ConclusionThe strength of the nGenius Solution is its ability to allow network managers and telecom professionals treatvoice as just another managed application on the network.By properly placing probes to capture critical voice flows, the nGenius Solution can collect even shuffled andhairpinned call data to deliver comprehensive real-time and historic reports of all network-based applica-tions, even down to the individual call conversation statistics.Customer Example:A media company located in the Midwest upgraded the firmware on their network edge routers.However, shortly after the upgrade users at a remote location began complaining about sporadicvoice quality issues. The cause of the problem stumped the IT staff because without a performancemanagement solution all they were able to do was manually correlate the poor voice performancewith network events.Using the nGenius Performance Management System, the IT staff viewed the network link, and allapplications running over it, concurrent with voice calls from the remote location. Jitter, packet lossand DSCP code points for each individual user were viewed. By using side-by-side analysis andforensic data they quickly determined that during the upgrade, a router had been incorrectly con-figured to handle voice, leading voice to be delivered behind a daily FTP backup from that location.They then reprioritized to the proper settings.004-09-30
